Reverting build_requirements to previous versions

Next week when dependabot asks to update the versions
of our documentation tools let's ask it to stop tracking
them for the time being as the new suggested versions
are failing...

Signed-off-by: Luc Berger-Vergiat <lberge@sandia.gov>

docs/build_requirements.txt

@@ -1,6 +1,6 @@
-Sphinx==8.2.3
-furo==2024.8.6
-myst-parser==4.0.1
-sphinx-copybutton==0.5.2
-sphinx-design==0.6.1
+Sphinx==6.2.1
+furo==2024.4.27
+myst-parser==3.0.1
+sphinx-copybutton==0.5.0
+sphinx-design==0.5.0
 m2r2==0.3.2